Made it replacing the lemon with straight white vinegar (as a friend is allergic to citrus). It is very good, but for me -- very spicy. I doubled the recipe and it worked quite well. The spiciness isn't quite cut enough when you mix it with greek yogurt; but it helps.
BTW -- doubling it made 2 750ml mason jars full of soup + fed 5 people a bowl each (with another couple of bowls left-over).